Effect of surfactant concentration, compression ratio and compression rate on the surface activity and dynamic properties of a lung surfactant.

This paper reports dynamic surface tension experiments of a lung surfactant preparation, BLES, for a wide range of concentrations, compression ratios and compression rates. These experiments were performed using Axisymmetric Drop Shape Analysis-Constrained Sessile Drop (ADSA-CSD). The main purpose of the paper is to interpret the results in terms of physical parameters using the recently developed Compression-Relaxation Model (CRM). In the past, only the minimum surface tension was used generally for the characterization of lung surfactant films; however, this minimum value is not a physical parameter and depends on the compression protocol. CRM is based on the assumption that the dynamic surface tension response is governed by surface elasticities, adsorption and desorption of components of the lung surfactant. The ability of CRM to fit the surface tension response closely for a wide variety of parameters (compression ratio, compression rate and surfactant concentration) and produce sensible values for the elastic and kinetic parameters supports the validity of CRM.